Coupling



FIG. 1 is a front elevational view of a coupling embodying my new design, the rear being a mirror image of the front shown;

FIG. 2 is a top plan view thereof, the bottom being a mirror image of the top shown;

FIG. 3 is a left end elevational view thereof; and

FIG. 4 is a right end elevational view thereof. 

The ornamental design for a coupling, substantially as shown and described. 